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1.
本研究以番茄–黄瓜轮作下的设施土壤为研究对象，共设4个处理（1/2化肥氮+1/2生物有机肥氮，COF；全部施用生物有机肥氮，OF；全部施用化肥氮，CF；不施肥处理，CK），探讨生物有机肥配施化肥对设施土壤养分含量及团聚体分布和稳定性的影响。研究结果表明，相较于单施化肥处理，施用生物有机肥均提高了土壤有机碳、全氮、全磷、全钾、有效磷、速效钾养分含量和土壤pH，分别提高了9.61%~54.28%、7.38%~35.45%、31.86%~98.53%、40.88%~96.40%、3.02%~15.99%、0.96%~18.23%和0.73%~7.03%；单施生物有机肥或与化肥配施均可使土壤大团聚体（>0.25 mm）比例上升，微团聚体（<0.25 mm）比例下降，显著提高了土壤团聚体平均重量直径（MWD）、几何平均直径（GMD）和>0.25 mm团聚体含量（R0.25）（P<0.05），且土壤团聚体稳定性随着施入生物有机肥年限的增加而增加；相关分析表明，MWD、GMD和R0.25均与>2 mm和0.25~2 mm团聚体质量分数呈显著正相关（P<0.05），与<0.053 mm团聚体组成呈极显著负相关（P<0.01），与0.053~0.25 mm团聚体组成呈显著负相关（P<0.05）。生物有机肥替代化肥更有利于提高土壤养分含量、大团聚体的数量及团聚体的稳定性。 相似文献
2.
为探索施用有机肥对咸水灌溉农田耕层土壤水稳性团聚体的调控效应,在麦玉两熟制农田咸水灌溉(1,2,4,6 g/L)配施有机肥(OF)和未施有机肥(NOF)长期定位试验的基础上,研究了2018-2019年不同处理对农田耕层0-20 cm土壤盐度(EC1:5)、土壤有机质(SOM)含量和水稳性团聚体稳定性的影响。结果表明:咸水灌溉有增加耕层土壤盐度,降低SOM含量和水稳性团聚体稳定性的趋势,随灌溉水矿化度的升高,SOM含量、>0.25 mm水稳性大团聚体质量分数(WR0.25)、团聚体平均重量直径(MWD)和几何平均直径(GMD)逐渐减小,土壤EC1:5和分形维数(Dm)逐渐增大,其中4,6 g/L与1 g/L灌水处理间的差异达显著水平。增施有机肥可降低咸水灌溉农田0-20 cm土壤EC1:5,当灌溉水矿化度 ≥ 2 g/L时,OF处理的耕层土壤EC1:5较NOF处理降低4.64%~48.29%;施用有机肥显著提高农田SOM含量、WR0.25、MWD和GMD,各灌水处理的提高幅度分别为80.75%~127.32%,10.36%~90.44%,12.90%~129.11%和11.88%~81.57%。在该研究条件下, ≥ 4 g/L咸水灌溉会显著增加土壤盐度,降低有机质含量,破坏土壤团粒结构,应谨慎使用;施用有机肥能促进耕层土壤盐分淋洗,降低盐分对土壤环境的负面影响,有助于实现咸水资源安全高效利用。 相似文献
3.
试验研究了不同筛分方法下生物质炭施用对土壤团聚体的影响,为生物质炭农业利用提供理论依据。设置生物质炭用量4个水平(0,10,20,30 t/hm2),氮肥用量2个水平(0,150 kg/hm2),通过2年田间定位试验,测定分析干筛法和湿筛法0—30 cm土层土壤团聚体分布及稳定性。结果表明:2种筛分方式下,不同处理各粒级土壤团聚体分布趋势基本一致,干筛法所得机械土壤团聚体主要以＞5,2~5 0.5~1 mm粒级为主,而湿筛法水稳性团聚体均以0.25~0.5 mm及＜0.25 mm为主;不同处理干筛法土壤团聚体平均重量直径(MWD)、几何平均直径(GMD)均高于湿筛法。湿筛法下各处理,无论施氮与否,MWD、GMD均随生物质炭量增加而增大。其中,B0N0处理MWD、GMD最小,单施生物质炭B3N0处理土壤团聚体直径最大,分别较B0N0显著提高60%(MWD)和52%(GMD);各处理土壤团聚体破坏率(PAD)随生物质炭量增加而减小,土壤团聚体稳定率(WASR)则随生物质炭量增加呈上升趋势;干筛法各处理分形维数(D)均低于湿筛法,随生物质炭量增加D值不断降低,B3生物质炭量下分形维数最低,分别为2.63(B3N0)和2.64(B3N1),分别较对照降低3.3%和2.9%;分形维数(D)与＞0.25 mm土壤团聚体含量(R＞0.25)呈显著负相关关系。试验条件下,生物质炭添加量为30 t/hm2时土壤团聚体稳定性最佳。同时,湿筛法较干筛法能更好地模拟大田环境,真实反映土壤团聚体分布及其稳定性。 相似文献
4.
优化施肥方式对黄土高原新增耕地土壤有机质含量和团聚体特性的影响 总被引：1，自引：0，他引：1
[目的] 研究优化施肥对黄土高原地区新增耕地土壤质量和作物产量的影响,为新增耕地土壤建立合理的优化施肥处理和区域新造土地的健康可持续发展提供理论依据。[方法] 通过盆栽种植试验,评估有机肥处理（OF）、有机肥配施化肥处理（NP）、常规施肥处理（CF）对新增耕地土壤团聚体数量、结构稳定性、有机质含量和玉米产量的改良效应。[结果] CF处理下新整治耕地土壤有机质含量最低为7.08 g/kg,土壤水稳性大团聚含量低,结构稳定性差。与CF处理相比,优化施肥方式下的OF和NP处理显著提高了新增耕地土壤有机质含量和玉米产量（p<0.05）,>0.25 mm粒级大团聚体含量和团聚体稳定性显著提升,其中OF处理对新整治耕地土壤团聚体数量和稳定性的改善效果最佳。在0—10 cm土层,OF和NP处理下土壤有机质含量分别为12.67,11.79 g/kg,比CF处理分别提高了46.2%和36.1%。OF处理下水稳性团聚体MWD,GMD,R0.25值分别比CF处理高了62.5%,21.4%和148.3%,分形维数比CF处理降低了1.7%;NP处理下水稳性团聚体MWD,GMD,R0.25值分别比CF处理高了18.8%,3.6%和40.9%,分形维数比CF处理降低了0.4%。在10—20 cm土层,OF和NP处理下土壤有机质含量、团聚体数量和结构稳定性也得到一定的提升。土壤有机质含量与团聚体平均重量直径（MWD）、几何平均直径（GMD）呈显著正相关关系（p<0.001）。[结论] 优化施肥是有利于提升新整治耕地土壤结构稳定性、保肥特性和土地生产力的有效措施。 相似文献
5.
在实验室条件下研究了浙中金衢盆地三个桔园土壤的持水特性、饱和导水率、蒸发强度及三种土壤结构改良剂对土壤团聚作用和蒸发强度的影响.结果表明,持水量与<0.01mm物理性粘粒含量呈正相关(r=0.933*);饱和导水率与团聚体平均重量直径呈正相关(r=0.956**),而与结构破坏率呈负相关(r=-0.996**).当土壤吸力在50-100kPa时,桔园就需灌溉.加入三种土壤结构改良剂后能明显改善土壤水稳性团聚体,其效果为聚乙烯醇>聚丙烯酰胺>水解聚丙烯腈;使土壤的日平均蒸发强度减少,其减少的顺序为黄筋泥>紫砂土>红砂土.土壤饱和导水率K10值紫砂土>黄筋泥>红砂土,主要取决于土壤水稳性团聚体的平均重量直径,二者呈正相关(r=0.956**). 相似文献
6.
探讨有机物料还田对冬小麦田温室气体排放特性的影响,对提高经济效应和环境效应有积极意义。本研究应用静态箱-气相色谱法对秸秆还田（J）、秸秆还田+牛粪（JF）和秸秆还田+菌渣（JZ）3种有机物料还田下分别施氮肥243 kg （N）·hm-2（减氮10%,N1）、216 kg （N）·hm-2（减氮20%,N2）对冬小麦农田N2O、CO2和CH4的排放通量进行监测,探讨了不同施肥措施对麦田温室气体累积排放量、增温潜势的影响。试验期间同步记录每项农事活动机械燃油量、施肥量和灌溉量,测定产量,地上部生物量,估算农田碳截留。结果表明,冬小麦农田土壤N2O和CO2是排放源,是CH4的吸收汇,氮肥施入、灌溉以及强降水促进了土壤N2O和CO2的生成,却弱化了CH4作为大气吸收汇的特征。牛粪+秸秆（JF）处理N2O和CO2排放总量最高,分别为3.5 kg （N2O-N）·hm-2和19 689.67 kg （CO2-C）·hm-2,但CH4的吸收值最大,为5.33 kg （CH4-C）·hm-2,均显著高于菌渣+秸秆（JZ）和秸秆（J）处理（P<0.05）;各处理N2O和CO2的总量随施氮量的增加呈升高趋势,CH4的总量随施氮量的增加而呈降低趋势。JFN2、JN2和JZN2处理农田综合增温潜势（GWP）均为负值,表明有机物料还田且减氮20%条件下农田生态系统为大气的碳汇,麦季净截留碳1 038~2 024 kg·hm-2,其他处理GWP值均为正。JZN2处理小麦产量为8 061 kg·hm-2,显著高于JFN2处理（P<0.05）。综上所述,JZN2处理不仅能够保证小麦产量,且对环境效应最有利,为本区域冬小麦较优的施肥管理模式。 相似文献
7.
本研究以太湖地区稻田为研究对象开展连续两年的田间试验，通过设置不施氮肥（CK）、常规施氮（CN）、减氮表施（RN）、减氮侧深施（RNS）和减氮穴施（RNP）5种施氮处理，探究不同深施方式对稻田氨挥发与氮肥利用率的影响。结果表明，与表施处理（CN和RN）相比，RNS和RNP通过降低田面水NH4+-N浓度和pH分别减少30.95%~41.54%和66.71%~72.23%的氨挥发排放（P<0.05）。相较于RN处理，RNP促进水稻根系生长并增加根区土壤有效氮含量，进而增加水稻产量（6.23%），提高氮肥利用率（50.15%），降低土壤氮盈余（63.92%）（P<0.05）。与CN处理相比，RNS显著降低土壤氮盈余（29.20%）（P<0.05），但水稻吸氮量和氮肥利用率均未显著增加。相较于RNS，RNP进一步降低氨挥发损失（50.84%）和土壤氮盈余（51.07%），提高氮肥利用率（40.40%）（P<0.05）。综上所述，RNP的农学和环境效益最高，但因穴施机械及肥料造粒技术等因素的限制，尚难应用于实际生产；而侧深施肥在我国水稻大规模集约化生产中效益较高且切实可行。 相似文献
8.
为探究未经脱抗预处理的抗生素菌渣作为单一底物厌氧无害化处理的可行性,该研究以新鲜的红霉素菌渣（erythromycin fermentation residue,EFR）及其上清液为原料,在常温（20 ℃）、中温（35 ℃）和高温（55 ℃）条件下开展产气潜能及其动力学研究。研究结果表明：中温条件下,EFR获得最高的累积甲烷产量,为460 mL/g,比常温和高温时分别提高了163%和55.5%.通过一级动力学模型可以看出,EFR的产甲烷过程呈现明显的两阶段特性,其中高温时的产甲烷速率（ k1 =0.1 422 d-1）显著高于常温（k1 =0.0 429 d-1, P<0.05）和中温（k1 =0.0 363 d-1, P<0.05）。物料衡算分析显示,随着发酵温度的升高,EFR的水解转化率逐级提高,高温时最高为87%,表明高温条件下菌渣中残留的红霉素对水解菌基本未产生抑制作用。未经脱抗处理的EFR可直接作为厌氧发酵的原料,为菌渣的减量化和资源化处理提供了新的思路。 相似文献
9.
为探讨磁化水灌溉处理在促进植物生长、提高植株重金属耐受性方面的作用机制,本研究采用随机区组试验设计,研究了镉胁迫（0 μmol·L-1、50 μmol·L-1、100 μmol·L-1）下磁化水灌溉处理对1 a生欧美杨''I-107''光合特性、叶绿素荧光动力学参数及生长特性的影响。结果表明：1）镉胁迫会显著降低植株高生长和根茎叶干物质量;低浓度（50 μmol·L-1）镉处理促进根系直径及体积增大（P<0.05）,高浓度（100 μmol·L-1）则会抑制根系各形态参数;镉胁迫下欧美杨叶绿素b和类胡萝卜素含量分别降低12.50%、43.24%和19.27%、46.37%（P<0.05）,净光合速率（Pn）、蒸腾速率（Tr）、胞间二氧化碳（Ci）分别降低13.68%和33.68%、8.07%和27.81%、5.00%和14.99%（P<0.05）,同时,PSⅡ潜在活性（Fv/Fm）、最大光化学速率（Fv/Fo）、光合性能指数（PIabs）和量子产额（φEo）均有不同程度降低。2）磁化水灌溉提高镉胁迫植株高生长及根茎叶干物质量,增加植株根系长度及表面积;同时,叶绿素a、叶绿素b和类胡萝卜素含量在0 μmol·L-1和100 μmol·L-1镉胁迫下分别提高16.99%、40.20%,8.67%、39.10%和17.32%、50.52%（P<0.05）;Gs、Ci及WUE显著升高,Tr则降低24.20%、23.33%、12.06%（P<0.05）;另外,Fv/Fm、Fv/Fo、PIabs显著升高（P<0.05）。综上所述,磁化水灌溉处理有助于提高镉胁迫下欧美杨幼苗光合色素含量,维持光合机构功能,增强光合碳同化速率,减轻镉胁迫对植株生长发育的抑制。 相似文献
10.
[目的] 探究片蚀泥沙轻组有机碳(LFOC)和重组有机碳(HFOC)不均匀富集的水动力学和碳同位素特征,为正确理解水蚀作用下土壤有机碳库变化提供理论与技术支撑。[方法] 以陕西省咸阳市杨凌区土为研究对象,采用改进"三区"移动式变坡钢制土槽,结合人工模拟降雨技术,测定径流水动力学参数和泥沙各粒径团聚体有机碳组成及其δ13C值,并辅以棕壤侵蚀泥沙有机碳δ13C值和水力参数,验证土试验结果的准确性。[结果] ①雨强和坡度较小时,侵蚀泥沙LFOC和HFOC易发生富集,且相较黏粉粒和微团聚体,大团聚体LFOC与HFOC含量受雨强和坡度的影响更大; ②侵蚀泥沙黏粉粒中有机碳δ13C值与其有机碳活跃分数(λ)呈负相关,而其他粒径团聚体有机碳δ13C值与其λ呈显著正相关(p<0.05); ③流速与黏粉粒λ显著正相关(p<0.05),雷诺数与各粒径团聚体有机碳δ13C值均呈显著负相关(p<0.01),片蚀过程中流速越大,黏粉粒中LFOC越易于优先输移,而紊流加剧则促进低δ13C值团聚体有机碳的优先输移; ④对于侵蚀泥沙黏粉粒,流速和雷诺数越大,其有机碳δ13C值越小,λ越大;对于微团聚体和大团聚体,雷诺数越小,其有机碳δ13C值与λ越大。[结论] 片蚀过程中轻重组有机碳流失与流速和雷诺数密切相关。并进一步验证了13C同位素对侵蚀泥沙有机碳示踪的有效性。 相似文献
11.
T. B. S. Christopher A. M. Mokhtaruddin M. H. A. Husni M. Y. Abdullah 《Soil & Tillage Research》1998,45(3-4):287-297
Wet-sieving method using nested sieves is one common method to measure aggregate stability. However, this method cannot be used to measure the stability of individual aggregate size fractions, only of whole soils. Thus, this study was to develop an equation to estimate the aggregate breakdown of individual aggregate size fractions in this particular method. The key to develop the equation was to assume that aggregate breakdown happens sequentially and consistently, and that the aggregate breakdown between any two aggregates in the same aggregate size fractions is equal in percentage. Applying these two assumptions, this equation was developed: xi=(Wai×Di)/(Wai+Di−1), where xi is the weight of aggregate breakdown in aggregate size fraction i, Wai is the weight of the aggregates in aggregate size fraction i before wet-sieving, and Di and Di−1 are the weight of aggregates that have passed through sieve i and i−1, respectively. This equation was tested with five soil series. The soils were separated into six aggregate size fractions: 4.76–8.0, 2.83–4.76, 2.0–2.83, 1.0–2.0, 0.5–1.0 and 0.3–0.5 mm. For every soil, each of their aggregate size fraction was separately wet-sieved to determine the actual aggregate breakdown. The separate wet-sievings results were then combined in such a way to simulate the usual wet-sieving method; that is, to construct the data that would have been produced if each of the aggregate size fractions was wet-sieved together in the same nested sieves. Paired sample t-test showed that the differences between the actual and estimated aggregate breakdown values were significant at 5%. However, there was very close correlation between the actual and estimated values (r=0.974; p<0.001); thus, the equation was calibrated by simple linear regression. The calibrated equation was:
i=100 sin2i, where
i is the calibrated breakdown estimate for aggregate size fraction i, and i is 0.0166xi+0.1 in unit radians. This calibrated equation was highly significant at 1% (F=766.039; p<0.001), with the values fitting very tightly along the regression line (R2=0.961), and with very small standard error (std. error=0.023). The calibrated equation was validated with three additional soils. Paired sample t-test showed there was insignificant differences between the actual and calibrated breakdown estimate values. Moreover, using fewer aggregate size fractions did not affect the accuracy of the calibrated equation, as this equation still predicted the actual values with very small errors. 相似文献
12.
Soils with high clay content are susceptible to structural damage, if they are intensively cultivated. The structure of soils of the Vertisol group has the tendency to restore as a result of wetting and drying. Samples of a remoulded clayey soil were exposed to seven successive wetting/drying (w/d) cycles, in order to study the change of some structural features of the newly formed aggregates. To assess the effect of soil water content and microbial activity, two different matric water potential ranges were used under sterile and non-sterile conditions.
Aggregate size distribution depended on both the water potential range and microbial activity and approached to a steady state with increasing cycle number. The water stability of the 2–1 mm aggregates was affected by the activity of soil micro-organisms under wet conditions and by forces of mechanical nature when the soil was reaching dryness. All cases resulted in aggregates of reduced water stability with respect to the natural aggregates. The <50 μm aggregated particles initially preserved stability, but after a number of w/d cycles they collapsed at a rate, depending mainly on the water potential range. 相似文献
13.
三峡库区坡地脐橙园保护性措施对土壤团聚体结构及碳、氮、磷含量的影响 总被引：2，自引：0，他引：2
依托三峡工程生态与环境秭归实验站的8 a长期试验,对5种保护性管理措施下坡地脐橙园土壤团聚体结构与团聚体碳、氮、磷含量分布特征进行了研究。结果表明,脐橙套种多年生白三叶草(CM)和脐橙园地面农作物秸秆覆盖(SM)处理表层土壤(0～5 cm)大于0.25 mm水稳性团聚体含量、团聚体平均重量直径(MWD)值、大于0.25 mm水稳性团聚体氮含量及SM处理表层土壤大于0.25 mm水稳性团聚体磷含量显著高于其他处理;脐橙套种黄花菜等高植物篱(CH)处理和脐橙园沿等高线埋设防渗膜(MM)处理表层土壤大于0.25 mm水稳性团聚体含量及CH处理的MWD值显著高于常规脐橙栽植(CK)和脐橙套种小麦-花生(PC)处理;与CK处理相比,PC处理大于0.25 mm水稳性团聚体含量、MWD值、团聚体碳含量和表层土壤团聚体氮含量没有显著变化,但5～20 cm土壤团聚体磷含量有升高趋势。团聚体MWD与大于0.25 mm水稳性团聚体和团聚体氮含量有极显著相关关系。 相似文献
14.
A new method for the analysis of aggregate disintegration in water was tested using aeolian sediment samples. The response of aeolian sedimentary aggregates to wetting and mechanical energy has important implications for the immobilization of aeolian sediments by rainfall and their susceptibility to post-depositional erosion by water. Repeated laser diffraction analysis of a single sample circulating in deionized water provides a detailed view of the changes in particle size distribution as aggregates disintegrate. This methodology also allows experiments on the effects of water chemistry, exchangeable cation chemistry, and prewetting. Results presented here suggest that aggregates of widely varying stabilities can occur in a wide range of particle size classes; that is, aggregate stability may to some extent be independent of the hierarchy of aggregate sizes emphasized in earlier research. The methods described here are broadly applicable to a variety of soils and sediments, but experiments are needed to relate the results more specifically to aggregate behavior under field conditions. 相似文献
15.
间歇性降雨对土壤团聚体粒级及磷、铜、锌富集的影响 总被引：3，自引：1，他引：2
探讨间歇降雨条件下土壤干湿交替对团聚体粒级动态变化的影响,对加深径流泥沙运移和分选机制的理解、揭示土壤微量元素随地表径流迁移的规律具有重要意义。通过37d内的5场间歇性人工降雨实验,观测了降雨激发的团聚体破碎过程和降雨间歇段干缩过程导致的团聚体粒径分布的动态变化,并通过分析不同团聚体粒级总磷、铜、锌含量的动态变化,评估了间歇降雨对土壤污染物富集特征的影响。结果表明,间歇性降雨导致的土壤干湿交替引发了剧烈的团聚体粒级周转,团聚体稳定性随实验推移呈总体退化状态,具体体现在250μm微团聚体的比例随实验推移显著下降,而250μm微粒的比例显著上升(P0.05)。团聚体粒径分布的变化引起了不同粒径磷、铜、锌含量的同步变化,三种元素从250μm向63μm粒级逐渐转移,造成63μm粒级内各元素浓度在实验末期达到最高,这意味着间歇性降雨引起的团聚体结构退化和250μm微粒的增加及微量元素富集会加大水土流失及伴随污染物排放的风险。本研究揭示了间歇性降雨引起的土壤团聚体结构变化及对泥沙分选和元素迁移过程的影响,为土壤侵蚀引起的横向物质运移机制提供了一定的理论参考。 相似文献
16.
Effect of raindrop impact and its relationship with aggregate stability to different disaggregation forces 总被引：3，自引：0，他引：3
A soil surface exposed to rainfall is subjected to processes of wetting and drop impact which can lead to the formation of a seal during the rainfall, reducing infiltration and increasing erosion by increasing runoff. The objective of this research was to evaluate the relationship between the effect caused by the drop impact and the aggregate stability of the soils when they are subjected to different disaggregation forces. The aggregates were subjected to cracking (by slow wetting), slaking (by fast wetting) and mechanical breakdown (by mechanical stirring after pre-wetting in ethanol). The effect of each process was evaluated by measuring the mean weight diameter (MWDsl, MWDf and MWDst, respectively) calculated as the sum of the mass fraction of soil left in the sieve after fractionation into four size classes, ranging from <0.25 to 2 mm, multiplied by the mean aperture of the sieve meshes and divided by the initial soil weight. The effect of water impact plus wetting was quantified by the saturated hydraulic conductivity of the seal (Ks) and the time necessary to reach this value. A relative sealing index (RSI) that measured the reduction of water intake caused by sealing was defined as the relationship between the minimum value of saturated hydraulic conductivity of the seal and that reached when the drop impact was avoided. The air-dry material rupture was evaluated with a penetrometer. The main soil characteristics that determine all these processes for the study soils were analysed. Most of the studied soils were very sensitive to slaking and mechanical breakdown, while they were stable when they were subjected to slow wetting. A significant relationship was found between the minimum saturated hydraulic conductivity (Ks) and the MWDst (R2=0.40, p<0.005), and between Ks and the MWDf (R2=0.69, p<0.05). In both treatments, slaking and mechanical stirring, the percentage of aggregates retained in the larger sieve mesh was also significantly correlated with Ks. This result could indicate that both processes are implicated in the disaggregation produced by drop impact, which contribute to seal formation process. The less stable soils had the lowest Ks value (<1 mm h−1), which was reached in a short period of time (<10 min). The high silt content and the low organic matter control the loss of aggregation by mechanical breakdown and the formation of the seal. The RSI values indicated a 200-fold reduction in water infiltration for some soils, caused by the formation of a seal. 相似文献
17.
This work investigates the distribution of soil aggregates for Vertisols and Ferrasols as a function of the actual energy involved in dispersion, known as the dispersive energy. For Vertisols showing an aggregate hierarchy, the breakdown of aggregates 2–50 μm is modelled using the aggregate liberation and dispersion characteristic curve indicating a stepwise breakdown of soil aggregates. Meanwhile, for Ferrasols, the breakdown of 2–50 μm aggregates increases monotonically with increasing dispersive energy, which is indicative of the direct release of silt and clay from the disruption of aggregates. For soils displaying an aggregate hierarchy, the relative rate constant of aggregate liberation is much larger than the relative rate constant of the aggregate dispersion. Furthermore, the redistribution of aggregates for a number of size ranges within the 2–50 μm fraction illustrates a number of different pathways in aggregate breakdown, and the assumption that aggregates follow an exponential decay may not detect the presence of a weakly expressed aggregate hierarchy. The exponential decrease in ultrasonic power over time for the Ferrasols, as opposed to the prominent drop or steps in the curves for the Vertisols, confirms the lack of a prominent aggregate hierarchy. 相似文献
18.
稻田垄作免耕对土壤真菌多样性分布的影响 总被引：1，自引：0，他引：1
在水田长期垄作免耕处理下,研究了土壤真菌多样性及其在不同大小团聚体中的分布.结果表明,垄作免耕处理下,耕层土壤中,真菌主要分布于粒级为1.0～0.25 mm的土壤团聚体中,同时在＞0.053 mm的各级土壤团聚体中垄作免耕处理下真菌数量多于常规轮作处理;垄作免耕处理的各级土壤团聚体中都有毛霉和根霉存在,且1.0～0.25mm土壤团聚体中属类最丰富,其simpson多样性指数为0.93,Shannon多样性指数为1.24,常规轮作下属类丰度没有明显变化.稻田垄作免耕提高了不同团聚体中真菌的数量、多样性,改变了真菌在不同大小团聚体中的分布状况. 相似文献
19.
生物质炭对稻田土壤团聚体稳定性和微生物群落的影响 总被引：1，自引：1，他引：0
土壤团聚体决定着土壤功能与质量,受土壤生物与非生物因素的共同作用。本文从非生物和生物学角度解析生物质炭施用对土壤团聚体稳定性的长期影响。以句容和南京两个独立施用生物质炭3年或5年后的稻田麦季土壤为研究对象,选取常规施肥（CK）和常规施肥+生物质炭（AB）处理,利用湿筛法获得不同粒级土壤团聚体,并测定其中有机碳（SOC）、全氮、全磷含量,同时采用定量PCR技术测定土壤微生物（细菌、真菌、丛枝菌根真菌、古细菌和放线菌）丰度。结果表明：句容和南京土壤AB处理生物质炭原位老化后,大团聚体比例（R>0.25）和土壤田间持水量显著增加,平均重量直径和几何平均直径表现出增加趋势（P>0.05）;土壤团聚体养分含量（SOC、全磷）和土壤微生物丰度发生显著变化。与对照处理相比,句容和南京老化生物质炭处理的土壤大团聚体比例分别显著增加93.0%和61.5%,0.002～0.053 mm和<0.002 mm粒级团聚体均呈减少趋势;句容和南京土壤AB处理全土SOC含量分别显著增加26.3%和26.9%,大团聚体中SOC含量分别显著增加72.4%和52.3%,微团聚体中SOC含量分别显著增加20.8%和30.0%,全土真菌丰度显著增加;南京土壤全磷含量显著增加25.4%,丛枝菌根真菌和古细菌丰度也呈增加趋势（P>0.05）。由相关性分析可知,土壤团聚体平均重量直径与大团聚体比例、SOC含量、真菌和丛枝菌根真菌丰度极显著正相关（P<0.01）,与全磷含量和古细菌丰度显著正相关,相关系数分别为0.641和0.646。综上所述：生物质炭可以改善土壤pH值,田间持水量等理化性质,增加稻-麦轮作麦季土壤0.25～2 mm大团聚体比例和碳、磷含量,增加土壤真菌、丛枝菌根真菌和古细菌丰度,提高土壤团聚体稳定性,具有持续性。 相似文献
20.
Diversification of production is a concern for farmers in many regions of the world, raising a renewed interest in crop-animal rotations. However little information is available on whether the introduction of grazing animals in a no-till system could be a sustainable practice. The present long-term study was carried out in the semiarid region of Argentina, on an Entic Haplustoll (A, AC, C and Ck profile). The experimental plots were established in August 1993, with two treatments, no-till (NT) and conventional tillage (CT). Stubble was regularly used for grazing until 2002, when plots were divided into grazed (G) and non-grazed (NG) sub-treatments. Soil samples were taken at 0–0.10 and 0.10–0.20 m depth at the beginning of the experiment (1993) and during 2007, with the following determinations: clay + silt contents, bulk density (BD), total carbon (C), total nitrogen (N), available P, C contents of aggregate fractions of 2000–100 (POC), 100–50 (IOC) and <50 (FOC) μm diameter, aggregate size distribution and mean weight diameter change. NT showed a strong effect on all analyzed soil attributes: it had higher total carbon stocks (NT 16.6 Mg ha−1 vs. CT 13.2 Mg ha−1) and higher amounts in all C fractions, even in FOC (11.3 Mg ha−1 vs. 9.2 Mg ha−1). For BD, we found no difference between NT and CT at the surface and an even lower value for NT at 0.10–0.20 m depth. Under NT no depletion of available P occurred, while CT lost about 23 kg ha−1. Grazing had a negative effect on BD when averaging BD data across tillage systems, while there was no effect on aggregate stability, and a positive one on the proportion of >8 mm aggregates (23.3% vs. 11.7% for CT G and CT NG, respectively). C stratification showed a differential effect of grazing: NT G had the highest index (1.31) and CT G the lowest one (0.98). Our results indicated that the introduction of grazing animals in NT crop systems would not be detrimental to soil conditions and quality, at least in semiarid conditions of Argentina. 相似文献